Acoustic telephone



(Model.)

H. WILLARDI Acoustic Telephone.

No. 238,140. A A Patented March 8,1881.

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UNITED STATES PATENT GEEICE.

HENDERSON WILLARD, OF GRAND RAPIDS, MICHIGAN.

ACOUSTIC TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 238,740, dated March 8,1881.

Application filed November 19, 1880.

To all whom it may concern Be it known that I, HENDERSON WILLARD, acitizen of the United States, residing at the city of Grand Rapids, inthe county of Kent, and State of Michigan, have invented certainImprovements in Acoustic Telephones, of which the following is aspecification.

This invention relates toacoustic telephones in which a line ot' wireconnects two vibrating diaphragms, either of which may receive ortransmit sound.

The said invention consists, principally, in the combination, with eachdiaphragm, of a niouth-and-ear piece having its rear t'ace in contact atall points with the front of said diaphragm, in order to 4insureclearness and accuracy of sound.

1t also consists in constructing each mouthand-ear piece with aninwardly-tlaring passage or chamber having straight sides inclined at anangle, which will cause all sound-waves received therein from thediaphragm to be reliected forward through the open front of theinstrumentwithout returning` to the diaphragm or the neighborhoodthereof.

It consists, finally, in the special devices for supporting theconnecting-wire, and in certain other improvements hereinafter setforth.

In the accompanying drawings, Figure l represents a vertical sectionthrough one of the transmitting or receiving instruments, arranged withits mouth-piece upward; and FiO. 2 represents a side view of a part ot'the connecting-wire and the devices for supporting the same.

A designates one of the receiving or transmitting instruments, (it beingadapted to either use,) which consists of a case inclosing a broad rearsound-chamber, a mouth-piece or ear-piece, B, and a diaphragm, C, thatseparates said chamber from the interior ot' said mouthpiece. Said casepreferably consists of a front part integral with said mouthpiece, and arear part, A', secured to said front part by screws h It. A transmittingor connecting wire, G, is attached at one end to one ot' said diaphragmsand at the other end to the other, the attachment being made in eachcase by means of a button, d, on the front of the diaphragm, and an eye,O, at the rear of the latter, said eye having a shank, which passes(Model.)

through said diaphragm and screws into said button.

The general construction of the telephone, as above indicated, is notbroadly new; but hitherto there have been spaces, chambers, or recessesinterposed between the front of the diaphragm and the rear portion orbase of the mouth-piece. Now the said mouth-piece becomes an ear-piecewhen the instrument is used for receiving a message, and there ought tobe perfect clearness, distinctness, and purity of tone in the messagesreceived through it. Such air chambers,spaces,or recesses between anypart of the diaphragm and the rear wall of the mouth-piece willinevitably cause a certain inequality and unreliability in thevibrations of the diaphragm and a partial deadening of tone andconfusion ot' sound. To obviate this serious defect l have caused therear wall or base, b, of my mouth-piece (it is also the front wall ofthe casing A) to tit at all points squarely against the front face ofdiaphragm C, said diaphragm being attached near its periphery to saidwall b by tacks n or other convenient fastenings. Then the soundwavespassing through wire C reach diaphragm C they are transmitted, by thecentral portion of the latter, to the space or passage within themouth-piece without any loss of 8o tone or confusion of sound. The wallb adbrds at all points, except within the central opening, a solid braceor backing for said diaphragm.

The construction oi' my mouth-piece is another important feature ot' myinvention. This mouth-piece (or ear-piece) consists of anoutwardly-flaring part, f, and an inwardly-flaring part, ff', which forma shell or casing for two communicating chambers or passages, f j",which have the shape oftruncated cones placed with their lesser ent stogether, so as to form a neck, fm. The outer chamber, j", has a widetlare, so as to accommodate a persons mouth or ear readily and fully.Theinner one ares less, the sides having such an inclination that thewaves of sound thrown against the same, by the action of the diaphragmin receiving, will not be reliected back to said diaphragm nor acrossfrom side to side, but out of the instrument through the neck fm and thechamber or passage f. This avoids the confusion IOO and indistinctnessof sound due to vibrations from side to side of the ear-piece B and backtoward diaphragm O, which must inevitably arise when the chambercorresponding to f has curved walls, or even straight walls of too greatan inclination. The curved walls are, however, more objectionable thanthese last, since they tend to concentrate or focalize the sound-waveson the center of the diaphragm.

In sending` a message a part of the soundwaves caused by the voice willbe reected by the inclined sides of space f through neck fm against theinner face of the wall off', whereby they will again be reflected inconverging lines on the center of the diaphragm, so as to strengthen thesound without confusing it. Another portion of the sound-waves will passdirectly through neckf/H to diaphragm C without any reiiection whatever.Said diaphragm consists of two wooden strips or veneers, a and a',arranged with the grain of one crossing that of the other. This crossgrain arrangement lessens the liability to warp or split. Two strips,united as shown, give greater elasticity and resonance than a singlepiece of equal thickness. I t-hus combine in my diaphragm thehighestdegree of durability and resonance consistent with a givenquantity ofthe proper material.

To prevent sagging of the line-wire C', and impediment of longitudinalvibrations therein, and to maintain equality of tension at all points, Iemploy a number oi' supportingsprings therefor, hung at suitableintervals, and having the construction shown in Fig. 2. Each of thesesprings has a central eye, y, and two arms, s s', that extend therefromin opposite directions, the whole being formed from one bar ofspring-wire. Eye y is suspended by a wire, l, from any suitable iixeddevice, and the ends of arms s s are connected, by suspending-wires x',to two diiierent points on line-wire C', said line-wire being free,however, to slide through eyes or loops formed on the lower end of saidsuspending-wires. Arms s s tend constantly to rise into the positionindicated in dotted lines, thus lifting said wire and maintaining iteverywhere under equal tension. If the spring-support were at one pointofthe wire only the angle formed there in would necessarily be moreacute than those formed by my double spring-support above described, andthe transmission of the sound would be more or less impeded thereby.

Having thus described my invention, what I claim is- 1. The combinationof a diaphragm for transmitting and receiving sound with the rear faceofthe base of the mouth -and-ear piece, the greater part of saiddiaphragm being in contact with said rear face, for the purpose setforth.

2. In combination with a diaphragm for rcceivin g and transmittingsound, a mouthandear piece having its interior formed ot' two straightsolid communicating conoidal chambers, substantially as set forth.

3. A spring-bar, forming loop y, and arms s s', in combination withline-wire C and sus pending-wires Z m w.

HENDERSON VILLARD.

Witnesses:

EDWARD TAGGART, HENRY H. GIBSON.

